The invention relates to rotating abrasive drums used for sanding or polishing. More particularly, the invention relates to an apparatus for tensioning an abrasive belt against the surface of a rotatable drum so that it is securely held against the drum.
The present invention relates to an abrasive drum that carries on its outer surface a band of abrasive material, so that when the drum is rotated it is useful for sanding or polishing. Such abrasive drums are used for a variety of applications, including coarse sanding, finish sanding, grinding, rough polishing, and dry finishing.
Such drums typically retain abrasive materials in one of two ways. The first type incorporates an expandable drum onto which an abrasive sleeve is fitted. The second type of drum features a slot in the outer surface of the drum through which the ends of a sheet of abrasive paper or abrasive cloth are inserted and retained. Unfortunately, there are problems with both types of drums.
Expandable drums require the use of expensive abrasive sleeves that are sized to fit only a single size of drum. Even though the sleeves are fitted appropriately, the abrasive sleeves will still slip against the drum, particularly when the friction of the sanding or polishing exceeds the friction between the sleeve and the drum.
Drums that utilize abrasive sheets typically include an axial slot in the outer surface of the cylinder through which the two ends of the abrasive sheet are inserted. Typically some type of clamp or clip is placed within the cylinder itself to secure the ends of the abrasive sheet. However, even if the ends are securely fastened, wear and tear on the sheet result in gradual slackening of tension and slipping of the abrasive on the drum, typically resulting in tearing of the abrasive sheet.
Some abrasive drums have included elaborate internal mechanisms for tensioning the sheet of abrasive. However such tensioning apparatus are generally complicated, incorporating springs and counterweights, and often relying upon the centrifugal force that is exerted when the drum is spinning to maintain tension on the abrasive band. Such mechanisms tend to complicate the process of changing abrasive bands.
In contrast, the abrasive drum of the invention permits a wide variety of abrasive band sizes to be fitted snugly to a single size drum. Abrasive bands can be changed simply and quickly. Further, once fitted to the drum, each band is held snugly, and the appropriate band tension is maintained even when the drum is at rest.
The present invention includes a drum suitable for polishing or sanding a workpiece. The drum incorporates an internal expansion member disposed adjacent to and in communication with an axially extending slot in the cylindrical surface of the drum, configured so that when an abrasive belt is fitted to the exterior cylindrical surface so that a loop of the band is inserted through the axially extending slot and disposed around the internal expansion member, subsequent expansion of the member tensions the abrasive band against the surface of the drum, holding it securely.
The invention includes the drum of the invention, a method of applying an abrasive band to the drum of the invention, a sander or polisher that incorporates the drum of the invention, and a method of using the drum of the invention to grind, shape, polish, sand, or otherwise modify the surface of a workpiece.